Ngoepe, PE and Catlow, CRA. 2005. Computational modelling in materials at the University of the North. South African Journal of Science, vol. 101, 10 September, pp 475-479

Abstract:

The authors review computational modelling studies in materials resulting from the National Research Foundation-Royal Society collaboration. Initially, investigations were confined to transport and defect properties in fluorine and oxygen ion conductors used mainly in energy storage devices. Subsequently, the programme was broadened to include the themes of minerals, metal alloys, and polymers. Electronic and structural properties and voltage profiles of lithium battery electrodes with spinel, graphite, and chalcogenide structures were studied on energy storage devices. Similar properties have been investigated in the new magnesium-based chevrel structures. Calculations on the electronic and structural characteristics of precious metal and transition metal sulphides have also been carried out. In particular, new robust interatomic force fields have been derived, thereby enabling bulk and surface atomistic simulations of large systems including ilmenite, apatite and electrolytic manganese dioxides. Phase stability studies of light metal alloys, such as AlRe and MgLi, have been conducted and transformations followed amongst competing phases of Pt3Al. Cluster expansion methods were applied to Pt alloys for the generation of databases needed in the derivation of phase diagrams. We have also studied surface interactions of PtAl2 with sulphur and oxygen molecules. Semi-empirical potentials of gold were used to investigate the gold nanoclusters, in conjunction with ab initio methods. A fourth theme involved studies of polymers in which transport of small gas molecules and silicone oils in polysiloxanes were investigated. The wetting of nafion membranes and cellulose structures is now being studied for various applications. Spectroscopic methods have been used in part to complement theoretical calculations. We also report on the management and outcomes of the programme to date.